In-line skates of the prior art typically comprise a plurality of rotatable wheels fixed in place in a common line relative to a skate boot that receives a skater's foot. The wheels normally have a common tangent such that all wheels will contact a flat surface when the in-line skate rests thereon. With such a construction, a skater will tend to be propelled in a given direction by orienting the skate transverse to the desired direction of travel and applying a lateral driving force to the skate primarily with the skater's leg muscles.
As one knowledgeable in the art will be aware, propulsion is most effectively achieved when the plurality of wheels of the in-line skate are all in contact with the ground surface on which the skater is propelled. With a plurality of wheels in contact with the ground, the leg enjoys a stability that allows it to drive with virtually unlimited force with little or no effort required for stabilizing the skate.
However, the experienced skater will be aware that it is substantially impossible for a skater to keep all wheels of such an in-line skate in contact with the ground surface over the entire skating stroke. Doing so is particularly problematic during the final phase of leg extension. As the leg enters its final stage, the rear wheels of the skate inevitably will follow the skater's heel in lifting off of the ground surface. With this, since the wheels are fixed in position relative to the skater's foot, only the foremost wheel remains in contact with the ground whereby it becomes the skater's only means of applying a driving force to the ground. This is plainly evidenced by the uneven wear that the wheels of the in-line skate typically exhibit wherein the foremost wheel normally demands replacement well before the useful lifetime of the rear wheels has expired.
Unfortunately, the effects of a skater's being unable to keep all wheels in contact with the ground over the entire skating stroke go well beyond mere uneven wheel wear. What for most will be considered a far more important repercussion is that a skater is resultantly unable to transmit all available energy from the skater's leg to the ground surface. Instead, as the rear wheels are lifted off the ground and only the front wheel remains in contact with the ground for driving the skater, stabilizing the skater's leg, and enabling other performance characteristics required for most effective propulsion.
Similar disadvantages have been addressed relative to ice skates, for example, by designing blades with convex formal edges so that an increased blade surface will have contact with an ice surface at the end of the skating stroke. Furthermore, ice skates have been developed that allow a pivoting of the skate blade relative to the skate boot about an axis adjacent the toe end of the skate whereby the skate blade exhibits improved contact with the ice surface over final phase of leg extension. As one knowledgeable regarding the sport of speed skating will be well aware, this construction has proven to be a decided advantage over prior art fixed blade constructions.
However, attempting to produce a convex blade profile with in-line skate wheels would require superfluous weight in wheels that would have only relatively minimal contact with the ground. Also, the convex wheel distribution would be easily upset with the rapid wearing typical of skate wheels and the uneven surfaces over which in-line skates must travel. Furthermore, attempting to provide an in-line skate with an all-wheel pivoting blade structure has proven to be unacceptable due to vibrations, undesirable weight and leg stress, and unmanageably complex mechanical requirements.
Advantageously, a number of inventors have endeavored to provide an in-line skate that overcomes these disadvantages. For example, U.S. Pat. No. 4,272,090 was granted to Wheat in 1981 for an in-line skate that has a pivoting front wheel bogie and a fixed rear wheel unit mounted separately to a shoe portion of the skate. The front wheel bogie is disclosed as having an axis of rotation located horizontally at a mid-portion of the skate and vertically well below the bottom of the shoe portion of the skate. With this, the skate is said to provide stable floor contact of the wheels on the front bogie even while the heel and thus the rear wheel unit of the skate is raised from the ground as would happen during the final portion of the skating stroke.
Another in-line skate designed with similar intention is disclosed in the 1997 U.S. Pat. No. 5,634,648 to Tonel et al. In this skate, a front body is rotatably coupled to a rear body, and a pair of wheels is rigidly coupled to each of the front and rear bodies. With this, during the final phase of the skating stroke, the front body will rotate relative to the rear body to allow the front pair of wheels to maintain contact with the ground thereby improving the skater's comfortability and the effectiveness of the skating stroke.
It must be recognized that these and other skating inventions certainly represent improvements in the art of in-line skating. For a number of reasons, however, even skates embodying these inventions are less than ideal. For example, by disposing the axis of rotation of the front wheel bogie horizontally at the mid portion of the skate and vertically displaced below the bottom of the shoe portion of the skate, skates such as the skate of the '090 patent compromise the effective length of the skating stroke. The rearward horizontal location of the axis of rotation of the front wheel bogie naturally results in the front wheels being disposed posteriorly along the skate from the outset. With this, the skating stroke is abbreviated. Furthermore, the vertically displaced location of the bogie's axis of rotation cause it to rotate rearwardly relative to the shoe portion of the skate during the final portion of the skating stroke whereby the front wheels move even farther back relative to the shoe portion thereby further abbreviating and reducing the effectiveness of the skating stroke.
Also, skates such as that disclosed in the '648 patent that have pivoting boot sections sacrifice the rigidity of the skate structure that is desirable for full force transmission from the skater's leg, through the skate, and to the ground. With this, energy is lost and most efficient propulsion is compromised. Furthermore, the pivoting boot structure is undesirably complex and vulnerable to wear and breakage.
In light of the foregoing, it is clear that there remains a need in the art for an in-line skate that overcomes the disadvantages of the prior art by providing a skate that enables optimal propulsion over an extended skating stroke.